Device for measuring the intensity and the frequency of the sound produced by flowing gravels in rivers and the like



.Fufiy 14, 193$. w U N DEVICE FOR MEASURING THE INTENSITY AND THE FREQUENCY OF T SOUND PRODUCED BY FLOWING GRAVELS IN Filed Jan. 22, 1954 HE RIVERS AND THE LIKE Fig. 4

Recorder Amplifier %m 2m INVENTOR.

Patented July 14, 1936 UNITED STATES PATENT OFFICE AND THE FREQUENCY OF THE SOUND PRODUCED BY FLOWING GRAVELS IN RIVERS AND THE LIKE Walter Tiirk, Karlsruhe, Germany Application January 22, 1934, Serial No. 707,863 In Germany January 21, 1933 1 Claim.

(Granted under the provisions of sec.. 14, act of March 2, 1927; 357 O. G. 5)

Flowing detritus produces anoise distinctly audible even by the naked ear. The pitch of sounds of this noise varies from hollow rumbling of coarse rubbles to soft murmuring of gravel or 5- sand. The timbre of sounds of the same is at a certain water velocity dependent on the grain size of a mixture of detritus or of. the individual grain sizes of which such a mixture is composed. The intensity of this noiseis determined by the quantity of detritus flowing through a determined section in' the unit of time.

The taking up of the noise can be eliected by a microphone lowered into the river or applied to the bottom of a ship. The microphone current having been reinforced by suitable means, for example a resistance amplifier, the noise can be heard for subjective estimation by a loudly talking apparatus: orcan: be taken up objectively according: to the methods of sound analysisby suitable devices, fo-r example-regarding its intensity by a photographic recording ammeter and regarding l its pitch and. timbre. of. sounds by a soundanalysis by means of an oscillograph.

For the purpose of. determination of the quantity of detritus flowing through in the unitoi time the measuring instrumentmay be calibrated point for point in that in. carrying. out. the measurement. samples of detritus. are taken at the same time and at the same..place,,so1 that a determined defiectionof the ammeter can be. coordinated to a determined weight of detritus. flowing through a determined section. in the unit of. time. In order to allow the comparison. of the intensities of noise taken. up at difterentpointsot ariver. section with as each other, the microphone must be suspended. always at the. same.- level above. the. river bed, sincethe intensity of the. noise is dependent on thethickness of the stream of detritus",

The calibration of the device'for the determina- 40 tion ofi the grain size of a detritus or of the different grain sizes of which a mixture of detritus is composed, may be carried out in such manner that in a laboratory the noises of a series of detritus of uniform or mixed composition of the 45 grains are taken up on definite test conditions and that then according to the methods of sound analysis the spectrum appertaining to each noise is ascertained, which spectrum appears in the form of a band spectrum.

50 The working out of the noise taken up by the microphone regarding to intensity, pitch and timbre of the sound and its comparison with the calibration values may be carried out immediately on board of the measuring ship, or the noises 55 may be taken up on record disks accordincg to known methods and worked out later on in the laboratory. The latter method has the advantage of such a considerable saving of time that it is possible tocarry out a reliable determination of the flowing through of the detritus even at short 5ihigh-water-swellings, this being impossible in known methods of measuring detritus movements.

The pitch and the timbre of the noise to be taken up are dependent not only on the grain size or sizes but also on the water velocity which 10.- therefore must always be measured simultaneously. This is effected by means of a hydrometric vane the number of revolutions of which in the unit of time gives a measure for the Water velocity. The transmission and the registration of 15-. the electric impulses furnished by the hydrometric vanemay be effected by superimposing these impulses on the microphone current.

Advantageously the hydrometric vane and its transmission and transformation organs are ap- 20v plied directly to the subaqueous microphone; for example. the hydrometric. vane is placed. at the head. of a. fish-bellied Weight, in the interior of Which the microphone and the organs controlled by the hydrometric vane are disposed. By the 25- described combination of the subaqueous microphone and the hydrometric vane the cables hitherto required for measuring the velocity together with the appertaining indicating instruments are spared. Owing to the synchronous 30 registration of detritus noise and water velocity in one and the same diagram the working out can be executed particularlyexactly and rapidly.

In carrying out the method in the manner above described the microphone body must be retained at a constant level above the always changing river bed. For this purpose the occasional depth of water at the measuring places must be established point by point by gaging; this: necessitates always acertain waste of time. However, the method can be accelerated and carried out continuously in the following manner:

Two fish-bellied weights each of, for example,

50 kg., in which a microphone is mounted, are suspended one above another in an observation slot of the measuring ship, for example in a water depth of 1 or 2 m. respectively. Furthermore a hydrometric vane is suspended on said ship at a certain distance below the water surface. If now the ship guided by suitable ropes is yawed over the whole measuring cross section, the measuring instrument furnishes two different curves of noise intensities and the appertaining water velocities. The noise intensity being inversely roportional to the quadrate of the noise as well as the occasional water depth for every point of the cross section. By simultaneously taking samples by a detritus catcher applied to the measuring ship a value of comparison of the detritus flow and the true noise intensity at a certain distance, for example of l m., from the bed is obtained. Thus, all Values necessary for the measurement, namely detritus quantity, water velocity and water depth, are obtained in a single operation.

Instead of causing the impulses of the two microphones to be automatically recorded by separate intensifier aggregates, it is advantageous for an absolutely uniform intensification to send the same alternatively in short intervals of time (for example of sec.) through a single intensifier. In this manner a rhythmically stepped meandrous curve of noise intensities is obtained. If now the switching-over from one to the other microphone is effected by the hydrometric vane always after a certain number of revolutions of the hydrometric vane, which is rotated by the flow of water with varying velocity according to that of the water, for example 50 revolutions, and a time signal is simultaneously recorded, for example once in each second, the appertaining water velocity can be read off by the rhythm of the steps of the curve. Moreover, a. further electric stand signal can be recorded simultaneously from a lateral rope capstan at certain distances, for example of 10 m., measured from a bank of the river.

My invention has for its object a device for carrying out the measurement in this manner.

In the accompanying drawing Figure 1 shows this device and Figure 2 shows on an enlarged scale a piece of sheet provided with a meanderline by the recorder forming part of this device.

In Fig. 1 HA and HB are two hydrophones (subaqueous microphones) which are suspended on a measuring ship (not shown) at constant but different distances below the water surface and adapted to be carried by said ship across the river section to be investigated. V is a hydrometric vane also suspended on said ship and serving for measuring the water velocity. A is an electric amplifying, rectifying and recording aggregate comprising an amplifier a, a rectifier b and a recorder c, and S are means operated by the vane V for periodically and alternately switching over the hydrophones HA and HB to the aggregate A after a constant number of revolutions of the vane V. These means comprise an electromagnetic ratchet device and a contact device. Said ratchet device is constituted by an electromagnet, the coil 11 of which is in the circuit of a battery 6 as is also the contact device f of a the vane V, and the armature g of which carries a pawl h engaging a ratchet-wheel i. Said contact device comprises a cam is connected to the wheel 12 and three contact springs 2, m and n. o is a battery, in the circuit of which are the hydrophone HA, the aggregate A and the springs Z and m, and p is a battery, in the circuit of which are the hydrophone HB, the aggregate A and the springs Z and n.

The electric impulses furnished by the hydrometric vane V cause the pawl h to rotate the wheel 1' together with the cam is in such manner that one revolution of these two parts corresponds toa certain number of revolutions of the vane V, for example 100, and always after half a revolution of the parts It and z' corresponding to, for example, 50 revolutions of the vane V the contact spring Z, the free end of which slides on the stepped periphery of the cam is, is moved by the latter so as to come out of contact with the free end of the spring m and in contact with that of the spring 12 or vice-versa. Thus, always after a. constant number of revolutions of the vane V, for example 50, the microphones HA and HB are alternately switched over by the devices hi and kZ-mn to the aggregate A so that the electric'impulses furnished by the two hydrophones are alternately sent through the aggregate. Consequently and as there exists a certain relation between the intensity of sound produced by the grains of gravel knocking together and the velocity of the streaming water, because the latter is the cause of the collisions of the grains, the recorder 3 produces on the record sheet a single curve in the form of a meander-lineas shown in Fig. 2. The length of the singular pieces of this interrupted line indicates the velocity of water, and the distance of two adjacent pieces indicates the intensity of sound belonging to this velocity.

What I claim as my invention and desire to secure by Letters Patent is:

A device for measuring the intensity and the frequency of the sound produced by flowing gravels in rivers and the like, comprising in combination two microphones for hearing the noise produced by the flowing detritus, said microphones being suspended on a measuring ship at constant but different distances below the water surface and adapted to be carried by said ship across the river section to be investigated, a hydrometric vane for measuring the water velocity,,an electric amplifying and recording aggregate, and means adapted to be operated by said hydrometric vane for periodically and alternately switching-over said microphones to said aggregate after a. constant number of revolutions of said hydrometric vane.

WALTER TURK. 

